Eye shape is the shape formed by the empty points of an eye. The size and shape of an eye can be crucial to the question of whether a second eye can be formed inside it. A play on the vital point of an eye shape that prevents the formation of a second eye is called a nakade.
Here are some standard eye shapes:
These eye shapes can be alive, dead, unsettled (killable with one move) or killable with more moves. See also